1. Field of the Invention
The present invention relates to a resilient connector for a steering shaft. Such a resilient connector is attached to an end of a steering shaft of an automobile vehicle for preventing the transmission of vibration applied to steering vehicle wheels to a steering handle. The connector is also adapted to absorb shock in order to ensure the driver's safety if a collision of the vehicle occurs.
2. Related Background Art
In a steering system for an automobile vehicle, the movement of a steering handle is transmitted to a steering gear through a steering shaft to provide a steering angle at steering vehicle wheels (normally, front wheels). In such a steering system, generally, since a transmission mechanism for transmitting the steering force from the steering handle to the steering gear is constructed mechanically, if the vehicle is running on a rough surface, the vibration applied to the steering wheels will be transmitted to the steering handle through the steering gear and the steering shaft. If the vibration is transmitted up to the steering handle, the driver feels uncomfortable for driving or steering the vehicle.
It is known that by providing a resilient connector at an end of the steering shaft to absorb such vibration, the vibration of the steering wheels may be prevented from being transmitted up to the steering handle. An example of such an arrangement is disclosed in Japanese Utility Model Laid-Open No. 61-191528 and is shown in FIGS. 3 and 4. In FIGS. 3 and 4, the reference numeral 51 denotes a flange fixed to an end of a shaft 52 which is connected to a steering gear. The reference numeral 53 denotes a coupling member made of elastic or resilient material such as rubber and the like. A resilient coupling is constructed to absorb vibration by the elasticity of the coupling member 53. The reference numeral 54 denotes a yoke opposed to the flange 51 with the interposition of the coupling member 53, which yoke 54 can be connected to the end of a steering shaft (not shown) through a universal joint (not shown).
The flange 51 and the coupling member 53 are connected to each other by first bolts 56 and first nuts 57 situated in diametrically opposed positions, and by a first connecting means comprising a first circular hold-down plate 58 having arcuate notches 71 cut therein in diametrically opposed positions. More particularly, the first bolts 56 passed through openings 59 formed in both end portions of the flange 51 pass through a pair of diametrically opposed through holes 60 among four through holes 60, 61 formed in the coupling member 53 equidistantly, and then pass through openings 62 formed in both end portions of the first hold-down plate 58, and thereafter threadedly receive the first nuts 57 thereon, respectively, whereby the flange 51 and the coupling member 53 are fastened to each other.
In addition, the yoke 54 and the coupling member 53 are connected to each other by second bolts 63 and second nuts 64 situated in diametrically opposed positions, and by a second connecting means comprising a second hold-down plate 65 like the above-mentioned first hold-down plate 58. More particularly, the second bolts 63 passed through openings 66 formed in both end portions of the base end of the yoke 54 pass through the remaining pair of diametrically opposed through holes 61, and then pass through openings 67 formed in both end portions of the second hold-down plate 65, and thereafter threadedly receive the second nuts 64 thereon, respectively, whereby the yoke 54 and the coupling member 53 are fastened to each other.
As a result, as shown in FIG. 4, the flange 51 fixed to the end of the shaft 52 and the yoke 54 are connected to each other through the coupling member 53 of elastic material. When the yoke 54 is rotated on the axis of shaft 52 through the universal joint and the steering shaft (both not shown) by rotating the steering handle (not shown), the rotational force is transmitted to the flange 51 through the coupling member 53, thus rotating the shaft 52 fixed to the flange 51.
Since the coupling member 53 is made of elastic material such as rubber and the like, if the angular displacement (rotation angle) of the yoke 54 is small, such angular displacement will be absorbed by the elastic deformation of the coupling member 53, thus preventing the rotational movement from being transmitted to the flange 51 (the angular displacement to be absorbed affords a "play" normally provided in the steering system). Also, if the vibration from the steering wheels is transmitted to the shaft 52, the coupling member 53 will absorb such vibration, thus preventing the yoke connected to the steering shaft from vibrating.
As is further shown in FIGS. 3 and 4, first sleeves 68 through which the first bolts 56 also pass are engaged by second notches 69 formed in the second hold-down plate 65, and second sleeves 70 through which the second bolts 63 also pass are engaged by first notches 71 formed in the first hold-down plate 58. Therefore, the displacements of the flange 51 and yoke 54 in the rotating direction are limited within ranges in which the respective sleeves 68, 70 can be shifted in the corresponding notches 69, 71. Accordingly, the coupling member 53 is not damaged or destroyed since it is not excessively deformed.
In addition to the above discussed problem of vibration transmission, steering systems also present a problem with respect to safety during a collision. In particular, if the front part of the vehicle is crushed in a collision, the rear end of the steering shaft will protrude rearwardly toward the passenger compartment of the vehicle.
Thus, in order to prevent the driver from being struck by the protruding steering shaft (secondary collision), it is desirable to design the steering system such that the shaft may collapse when subjected to the collision force or shock. For this purpose, it has been known to use a non-elastic collapsible joint or coupling at the connection portion between the end of the steering shaft and another part such as the steering gear.
A non-elastic collapsible coupling, however, cannot avoid the aforementioned problem of vibration transmission. Conversely, a conventional elastic coupling, while avoiding the problem of vibration transmission, offers little or no collapsibility and is therefore inadequate from the point of view of driver safety.